Should I use stencil for this?
You may create a procedural b&amp;w mask and use it as a factor for mixing different shaders. It requires some experimenting to do it right but give you the full control over the dots' shape and sharpness. You may also create a b&amp;w mask via Texture Paint mode.



PROCEDURAL MASK

Set up the material nodes as pictured below. Set up the texture coordinates to Object and play with the Mapping node settings to place the dot where you want. Set the Gradient Texture's mode to Quadratic Sphere. Use Color Ramp node to set its blurriness.


Now duplicate the nodes with Shift+D and mix them using MixRGB color node (Multiply). 


Play with the settings of the duplicated Mapping node to place the dot on the top part/other side of the object.


By repeating the process you'll get a b&amp;w mask for mixing the two shaders.

PAINTED MASK

Unwrap the sphere (I marked a seam along the vertical edge loop and then unwrapped). Go to Texture Paint mode and add a new Diffuse Color paint slot. Set the image color to pure white. In painting tools set the brush color to black and set the curve's type to line e.g. In Options bookmark uncheck the Occlude, Cull and Normal checkboxes to paint through the mesh. Paint the dots and save your image. Use it as a mask as in the procedural example above.



Here's the .blend: